# Will man ever reach the end of the universe?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by A Canadian, Jan 27, 2003.

1. ### Slacker47Paint it BlackRegistered Senior Member

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Smile and shoot yourself in the head because you have seen that there is no God. I cannot express my pure joy at the thought of the edge.

My friend said that when he dies, he wants to be ejected into space because eventually some alien race will find him and regenerate him. Its completely possible, I think, because there would not be any bacteria to decompose him. Although, space dust may cause erosion. Although, think about the possibility of being regenerated in 6 billion years (possibly somewhere beyond our galaxy)!!!!

3. ### BeerculesRegistered Senior Member

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While visible light was not around until 300,000 years after the BB, the same would apply if it had been since the very beginning. Just imagine an infinite universe. Since light travels at a finite speed, and the universe is expanding, there are regions in the universe from we will never be able to see light from. So while we can see only a small part of the whole universe, it is possible that universe as a whole is, and always has been infinite.

5. ### A CanadianWhy talk? When you can listen?Registered Senior Member

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know what! thats a really good idea

cept you might loss your genitals to a comet or something!

7. ### PersolI am the great and mighty Zo.Registered Senior Member

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Thanks... I'm going through some of the books and links suggested so I can learn a little more about this. There are still problems I see with this, but I'm assuming that they'll be addressed somewhere.

8. ### blobranaRegistered Senior Member

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The big bang was invented originally to redress two key problems in cosmology.

1) The horizon problem-- the Universe looks the same in all directions, there is uniformity of the background radiation. There has not been enough time since the Big Bang for light/information to travel across the Universe and back. So how do the opposite horizons know about each other?

2) The flatness problem-- this is the puzzle that the space-time of the Universe is (probably) flat, the Universe i imagine sits on the dividing line between eternal expansion and eventual re-collapse.

The flatness problem can be looked at using mass. The density parameter is a measure of the amount of gravitational attracting matter in the Universe, (omega ). It is defined in such a way that if space-time is exactly flat then Omega would equal 1. One of the big difficulties in cosmology was the fact that the actual density of the Universe today is very close to this critical. This is extraordinary because as the Universe expands the density parameter should move away from the critical value.

If the Universe starts out with the parameter less than one, omega gets smaller as the Universe gets older, but if it starts out bigger than one , omega gets bigger as the Universe gets older. The weird fact that omega is between 0.1 and 1 today means that in the first second of the Big Bang it was precisely 1 to within 1 part in 10^60! My gut feeling is that it is EXACTLY 1.
BTW another important feature of this is that there is a large amount of dark matter or energy in the Universe. Another is that the Universe was made flat by inflation.
(like the floor in your room is flat, but the earth is round...)

Inflation, in a short period of exponential expansion, caused the very early Universe, to blow-up to the size of what is now. The observable Universe was once a tiny region about the size of a grapefruit. This process would flatten out space-time to make the Universe smooth, and would also resolve the horizon problem.

BTW Another reason why theorists came up with the idea of inflation was to get rid of magnetic monopoles -- particles carrying isolated north or south magnetic fields, predicted by the old Grand Unified Theory (GUTs) but we havent seen any!(?) Standard models of inflation solve the "monopole problem" by arguing that the Universe grew from a quantum fluctuation so small that our universe probably just has one monopole.

The Universe we live in is like a hole in a foamy sea of superdense, exponentially expanding inflationary cosmic material, within which there are other holes. All kinds of bubble universes will exist, and it is possible to work out the statistical nature of their properties. But we can never physically contact these other universes.

Because very dense regions blow up exponentially quickly (doubling in size every fraction of a second), it turns out that the volume of all regions of the super-Universe with twice any chosen density is 10^10 million times greater than the volume of the super- Universe with the chosen density.
For any random density, most of the matter at that density is near the middle of an expanding bubble, with a concentration of more dense material round the edge of the bubble.

BTW this exponential expansion can be faster than the speed of c, as it is the fabric of space/time that is expanding.

Basically, it may mean that not only could we be living near the middle of a bubble universe, but that the density of the region of space we can see may be less than the critical density, compensated for by extra density beyond our visible horizon.

Observations by the Hubble Space Telescope have suggested that cosmological models, which require exactly the critical density of matter, may be in too low. (Perhaps solved by a double/ two inflationary periods?) .

Of course i assume that the parameter, which measures the rate at which the Universe is expanding, the Hubble Constant, really is a constant, the same everywhere in the observable Universe.
Perhaps the measured value of the "constant" may be different for galaxies at different distances from us. We may seem to live in a low-density universe in which both the measured density and the value of the Hubble Constant will depend on where these properties are measured!

Yes, It is true that about 300,000 years after the Big Bang, the temperature of the Universe had dropped sufficiently for electrons and protons to combine into hydrogen atoms,
p + e --> H.
From this time on-wards, radiation (photons) was effectively unable to interact with the background gas; it has propagated freely ever since, while constantly losing energy because its wavelength is stretched by the expansion of the Universe.
So we CAN look back theoretically back to that piont...

You can switch on your TV and the static you detect is the radiation of the Universe at a very early stage on what is known as the surface of last scattering'.
Photons are the cosmic microwave background . Unfortunately the beginning of the universe will not be televised.

The visible horizon is really a horizon of information. it is an illusion to those in the center of the sphere.

So if you go past this visible horizon eventually you will see the edge of this bubble universe .the transition face to the next bubble/ universe .

And if you go past this expanded foamy universes ultimately you will see nothing, the VOID.

9. ### BeerculesRegistered Senior Member

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You can't get past this foamy inflationary universe, because if you went far enough you'd end up where you started. Besides, if there is a void, it must have 4 spatial dimensions.

10. ### blobranaRegistered Senior Member

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It was a flight of imagination.
By definition this universe is separate from any other universe.
The boundary condition may even lie just outside the visual horizon , but we could never have any knowledge of it as all information is lost beyond OUR visual horizon.

11. ### BeerculesRegistered Senior Member

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Well if we're talking about inflation, our universe is not seperate from what lies outside our visible region. In fact, what would we would call a universe (perhaps with different laws of physics) is just one region of the universe as whole that....inflated. Kind of makes the term multiverse redundant.

12. ### blobranaRegistered Senior Member

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Sry, not putting the idea over clearly,

The universe grew exponentially, lets say 10^50 times. This leave our tiny visual universe in the midst(?) of a vast bubble .
.All the regions that could host our region of local space, excluding any density gradients and boundary phases are essentially the same.

for any observers at the extremities of our visual universe, the properties of space/time would appear the same as our properties of space time.
However,
The radius of each of the observers visual universes would be (say) 15 billion light years...therefore information about regions out side this are lost (due to the continual expansion of space/time)

13. ### BeerculesRegistered Senior Member

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Yes, that's true, but there's still no edge to the whole collection of bubble universes. Hence, no 3D void outside.

14. ### blobranaRegistered Senior Member

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Hehe , that was just one senareo...an infinite amount of bubble universes...
But i can also suggest that, perhaps though some sort of Darwinian principle, many/most bubbles universes that were created did not have the correct properties and (say) quickly collapsed back again...
perhaps the reason why our universe is so finely tuned is because if it were NOT, then we wouldnt exist.

Perhaps we ARE the only universe, the Creation of of which may have swamped or excluded the formation of all the other bubble universes...We will never KNOW for sure...

As for edges` , i can propose that it the boundary condition (4d) of this universe, but who knows if that is the boundary condition of the foamy universe sea senareo...

15. ### apoloRegistered Senior Member

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Beercules, 2-05-03- 8:21 am is right. Olbers Paradox was solved a long
time ago. Unfortunately i forgot the name of the guy who solved it
(he was quite famous for other reasons too) and the solution aplies equally to an expanding finite universe and a steady infinite universe.

M.J.

16. ### mr. BwoondewopsRegistered Member

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end of universe

if you think of the universe as concept, then it would never end, unless of course you can imagine its ending. then it would be finite.

17. ### BeerculesRegistered Senior Member

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342
I don't recall the paradox being solved for a static universe, at least not one that had existed forever. There were many attempts at this, such as using interstellar dust to block out the light, but they all failed.

18. ### everneoRe-searcherRegistered Senior Member

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At any point of time , we are (any point in space), at the edge of 4-dimensional Universe.

19. ### blobranaRegistered Senior Member

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Well pointed out!

This is the basis of quantum tunneling.